1. Field of the Invention
The present invention relates to a structural member with a metal shell and a method of making the same; and, more particularly, to a novel structural member fabricated by injecting concrete mortar into an elongated hollow thin metal shell, which is adapted to be used in combination with a base, a wall and other members.
2. Description of the Prior Art
In general, a structural member such as a pillar, column, post, pole, beam and the like is made of lumber, concrete, metal or their composites according to its appropriate use.
In particular, a structural member made of concrete has been widely used in the construction field because of its high compressive strength and economy. Also, it has an advantage that it can be easily made in various shapes by designing a diverse form of molds. However, such concrete columns and posts are not adapted to be employed in decorative articles due to their rough surfaces and poor appearances. Accordingly, additional finishing elements made of lumber and/or metal plates are required to refurbish the crude surfaces of the concerte members in order to employ them for sophisticated purposes.
Consequently, hollow metal structural members made of, e.g., aluminum, aluminum alloys, stainless steel, zinc plated steel, special steel, copper or copper alloys are increasingly employed in various structural members such as supporting columns, connecting bars, ornamental poles and the like because of their appearances, high corrosive resistance and easy workability. In such hollow metal members, relatively greater thickness is required to withstand a given load, thereby entailing a high material/manufacturing cost.
Therefore, there have been attempts made to reduce the thickness of such a hollow metal structure by way of forming in a section of the structure a bent or inwardly grooved shape and thereby increasing the bending strength and the moment of inertia of the metal structure. However, the manufacturing cost of such metal member still remains relatively high because the formation of a particular shape in the metal member adds further manufacturing steps. In particular, since the relative thinness of the metal member makes it vulnerable to a sudden external force.
Accordingly, various structural members have been developed with the specific view of improving their tensile and compressive strength.
For example, U.S. Pat. No. 836,673 to A. W. Ford teaches a metal column filled with concrete therein, including reinforcing metal tubes placed in the column at its weakest or breaking points and embedded in the concrete. In U.S. Pat. Nos. 1,934,260 and 1,971,051, there are provided structural members comprising a concrete core, a metal shell enclosing the core and plates mounted in both ends of the core wherein the plates transmit and distribute compressed loads over the concrete core.
U.S. Pat. No. 3,468,090 to L. Hermite discloses a reinforced concrete structure which comprises a concrete core, and a continuous metal reinforcement surrounding the concrete core, a high strength adhesive interposed between the surfaces of the core and the reinforcement.
Although the concrete structural members disclosed in the above prior patents may have been useful for the intended purpose, a metal shell of greater thickness is needed to manufacture such structural members which are used in large constructional structures, thereby increasing the manufacturing cost.
In U.S. Pat. Nos. 2,874,546, 3,333,808 and 4,910,940, there are provided various devices for securing concrete structural columns or posts to a base. However, in such securing devices, substantial labor is required to assemble the parts due to their complicated structures.